SQUAREXT Implementation

SQUAREXT is extremely simple. After standard housekeeping chores are completed (determining size, saving data segment, clearing playground), it extracts the sidelen, xoff, and yoff arguments, and then uses a for loop over the length of a side, filling in pixels with WHITE. The COORD macro translates cartesian coordinates into the index of the picture array.

#define COORD(x,y) (((y)+HEIGHT_CENTER)*WIDTH+((x)+WIDTH_CENTER)) ... sidehalf = sidelen / 2; for (i=-sidehalf; i<sidehalf; i++) { A[COORD(-sidehalf+xoff, i+yoff)] = WHITE; A[COORD( sidehalf+xoff, i+yoff)] = WHITE; A[COORD( i+xoff, sidehalf+yoff)] = WHITE; A[COORD( i+xoff, -sidehalf+yoff)] = WHITE; }